13. 'Sweet Dee's Dating a Retarded Person' (Season 3, Episode 9)
The title refers to the B-plot, where Dee lets Dennis' insults get under her skin and starts scrutinizing her rapper boyfriend Lil' Kevin to figure out if he's mentally handicapped. (Arguments for: He lives with his mom, he drinks juice boxes, and he hugs really hard.) But the real action happens when the men of Paddy's decide to form a rock & roll band, and then splinter into factions over disagreements about everything from their name — Frank favors the Pecan Sandies, which he swears is a double-entendre — to whether they should rehearse. In the larger Sunny mythology, this episode is important for introducing the idea that the illiterate simpleton Charlie is secretly a musical prodigy, who writes a sexually charged prog-rock song that will figure prominently in the fan-favorite "The Nightman Cometh."